summaryrefslogtreecommitdiff
path: root/trackerlogic.c
blob: 272539960d978d4ac4d9a55830cd5b251e1fca5f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
   It is considered beerware. Prost. Skol. Cheers or whatever. */

#include "trackerlogic.h"

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <time.h>
#include <math.h>
#include <glob.h>

#include <errno.h>
#include "scan.h"
#include "byte.h"
#include "mutex.h"

/* GLOBAL VARIABLES */

/* We maintain a list of 1024 pointers to sorted list of ot_torrent structs
   Sort key is, of course, its hash */
#define OT_BUCKET_COUNT 1024
static ot_vector all_torrents[OT_BUCKET_COUNT];
static ot_time   all_torrents_clean[OT_BUCKET_COUNT];
#if defined ( WANT_BLACKLISTING ) || defined( WANT_CLOSED_TRACKER )
static ot_vector accesslist;
#define WANT_ACCESS_CONTROL
#endif

static int clean_single_torrent( ot_torrent *torrent );

/* these functions protect our buckets from other threads that
   try to commit announces or clean up */
static ot_vector *lock_bucket_by_hash( ot_hash *hash ) {
  unsigned char *local_hash = hash[0];
  int bucket = ( local_hash[0] << 2 ) | ( local_hash[1] >> 6 );

  /* Can block */
  mutex_bucket_lock( bucket );

  return all_torrents + bucket;
}

static void *unlock_bucket_by_hash( ot_hash *hash ) {
  unsigned char *local_hash = hash[0];
  int bucket = ( local_hash[0] << 2 ) | ( local_hash[1] >> 6 );
  mutex_bucket_unlock( bucket );

  /* To make caller's code look better, allow
     return unlock_bucket_by_hash() */
  return NULL;
}

/* Converter function from memory to human readable hex strings */
static char*to_hex(char*d,ot_byte*s){const char*m="0123456789ABCDEF";char*e=d+40;while(d<e){*d++=m[*s>>4];*d++=m[*s++&15];}*d=0;return d;}

/* This function gives us a binary search that returns a pointer, even if
   no exact match is found. In that case it sets exactmatch 0 and gives
   calling functions the chance to insert data
*/
static void *binary_search( const void * const key, const void * base, const size_t member_count, const size_t member_size,
                            size_t compare_size, int *exactmatch ) {
  size_t mc = member_count;
  ot_byte *lookat = ((ot_byte*)base) + member_size * (member_count >> 1);
  *exactmatch = 1;

  while( mc ) {
    int cmp = memcmp( lookat, key, compare_size);
    if (cmp == 0) return (void *)lookat;
    if (cmp < 0) {
      base = (void*)(lookat + member_size);
      --mc;
    }
    mc >>= 1;
    lookat = ((ot_byte*)base) + member_size * (mc >> 1);
  }
  *exactmatch = 0;
  return (void*)lookat;
}

/* This is the generic insert operation for our vector type.
   It tries to locate the object at "key" with size "member_size" by comparing its first "compare_size" bytes with
   those of objects in vector. Our special "binary_search" function does that and either returns the match or a
   pointer to where the object is to be inserted. vector_find_or_insert makes space for the object and copies it,
   if it wasn't found in vector. Caller needs to check the passed "exactmatch" variable to see, whether an insert
   took place. If resizing the vector failed, NULL is returned, else the pointer to the object in vector.
*/
static void *vector_find_or_insert( ot_vector *vector, void *key, size_t member_size, size_t compare_size, int *exactmatch ) {
  ot_byte *match = binary_search( key, vector->data, vector->size, member_size, compare_size, exactmatch );

  if( *exactmatch ) return match;

  if( vector->size + 1 >= vector->space ) {
    size_t   new_space = vector->space ? OT_VECTOR_GROW_RATIO * vector->space : OT_VECTOR_MIN_MEMBERS;
    ot_byte *new_data = realloc( vector->data, new_space * member_size );
    if( !new_data ) return NULL;

    /* Adjust pointer if it moved by realloc */
    match = new_data + (match - (ot_byte*)vector->data);

    vector->data = new_data;
    vector->space = new_space;
  }
  memmove( match + member_size, match, ((ot_byte*)vector->data) + member_size * vector->size - match );
  vector->size++;
  return match;
}

/* This is the non-generic delete from vector-operation specialized for peers in pools.
   Set hysteresis == 0 if you expect the vector not to ever grow again.
   It returns 0 if no peer was found (and thus not removed)
              1 if a non-seeding peer was removed
              2 if a seeding peer was removed
*/
static int vector_remove_peer( ot_vector *vector, ot_peer *peer, int hysteresis ) {
  int      exactmatch;
  size_t   shrink_thresh = hysteresis ? OT_VECTOR_SHRINK_THRESH : OT_VECTOR_SHRINK_RATIO;
  ot_peer *end = ((ot_peer*)vector->data) + vector->size;
  ot_peer *match;

  if( !vector->size ) return 0;
  match = binary_search( peer, vector->data, vector->size, sizeof( ot_peer ), OT_PEER_COMPARE_SIZE, &exactmatch );

  if( !exactmatch ) return 0;
  exactmatch = ( OT_FLAG( match ) & PEER_FLAG_SEEDING ) ? 2 : 1;
  memmove( match, match + 1, sizeof(ot_peer) * ( end - match - 1 ) );
  if( ( --vector->size * shrink_thresh < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
    vector->space /= OT_VECTOR_SHRINK_RATIO;
    vector->data = realloc( vector->data, vector->space * sizeof( ot_peer ) );
  }
  if( !vector->size ) {
    /* for peer pools its safe to let them go,
       in 999 of 1000 this happens in older pools, that won't ever grow again */
    free( vector->data );
    vector->data = NULL;
    vector->space = 0;
  }
  return exactmatch;
}

static void free_peerlist( ot_peerlist *peer_list ) {
  size_t i;
  for( i=0; i<OT_POOLS_COUNT; ++i )
    if( peer_list->peers[i].data )
      free( peer_list->peers[i].data );
#ifdef WANT_TRACKER_SYNC
  free( peer_list->changeset.data );
#endif
  free( peer_list );
}

static void vector_remove_torrent( ot_vector *vector, ot_torrent *match ) {
  ot_torrent *end = ((ot_torrent*)vector->data) + vector->size;

  if( !vector->size ) return;

  /* If this is being called after a unsuccessful malloc() for peer_list
     in add_peer_to_torrent, match->peer_list actually might be NULL */
  if( match->peer_list) free_peerlist( match->peer_list );

  memmove( match, match + 1, sizeof(ot_torrent) * ( end - match - 1 ) );
  if( ( --vector->size * OT_VECTOR_SHRINK_THRESH < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
    vector->space /= OT_VECTOR_SHRINK_RATIO;
    vector->data = realloc( vector->data, vector->space * sizeof( ot_torrent ) );
  }
}

ot_torrent *add_peer_to_torrent( ot_hash *hash, ot_peer *peer  WANT_TRACKER_SYNC_PARAM( int from_changeset ) ) {
  int         exactmatch;
  ot_torrent *torrent;
  ot_peer    *peer_dest;
  ot_vector  *torrents_list = lock_bucket_by_hash( hash ), *peer_pool;
  int         base_pool = 0;

#ifdef WANT_ACCESS_CONTROL
  binary_search( hash, accesslist.data, accesslist.size, OT_HASH_COMPARE_SIZE, OT_HASH_COMPARE_SIZE, &exactmatch );

#ifdef WANT_CLOSED_TRACKER
  exactmatch = !exactmatch;
#endif

  if( exactmatch )
    return unlock_bucket_by_hash( hash );
#endif

  torrent = vector_find_or_insert( torrents_list, (void*)hash, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  if( !torrent )
    return unlock_bucket_by_hash( hash );

  if( !exactmatch ) {
    /* Create a new torrent entry, then */
    memmove( &torrent->hash, hash, sizeof( ot_hash ) );

    if( !( torrent->peer_list = malloc( sizeof (ot_peerlist) ) ) ) {
      vector_remove_torrent( torrents_list, torrent );
      return unlock_bucket_by_hash( hash );
    }

    byte_zero( torrent->peer_list, sizeof( ot_peerlist ) );
    torrent->peer_list->base = NOW;
  } else
    clean_single_torrent( torrent );

  /* Sanitize flags: Whoever claims to have completed download, must be a seeder */
  if( ( OT_FLAG( peer ) & ( PEER_FLAG_COMPLETED | PEER_FLAG_SEEDING ) ) == PEER_FLAG_COMPLETED )
    OT_FLAG( peer ) ^= PEER_FLAG_COMPLETED;

#ifdef WANT_TRACKER_SYNC
  if( from_changeset ) {
    /* Check, whether peer already is in current pool, do nothing if so */
    peer_pool = &torrent->peer_list->peers[0];
    binary_search( peer, peer_pool->data, peer_pool->size, sizeof(ot_peer), OT_PEER_COMPARE_SIZE, &exactmatch );
    if( exactmatch ) {
      unlock_bucket_by_hash( hash );
      return torrent;
    }
    base_pool = 1;
  }
#endif

  peer_pool = &torrent->peer_list->peers[ base_pool ];
  peer_dest = vector_find_or_insert( peer_pool, (void*)peer, sizeof( ot_peer ), OT_PEER_COMPARE_SIZE, &exactmatch );

  /* If we hadn't had a match in current pool, create peer there and
     remove it from all older pools */
  if( !exactmatch ) {
    int i;
    memmove( peer_dest, peer, sizeof( ot_peer ) );
    torrent->peer_list->peer_count++;

    if( OT_FLAG( peer ) & PEER_FLAG_COMPLETED )
      torrent->peer_list->down_count++;

    if( OT_FLAG(peer) & PEER_FLAG_SEEDING ) {
      torrent->peer_list->seed_counts[ base_pool ]++;
      torrent->peer_list->seed_count++;
    }

    for( i= base_pool + 1; i<OT_POOLS_COUNT; ++i ) {
      switch( vector_remove_peer( &torrent->peer_list->peers[i], peer, 0 ) ) {
        case 0: continue;
        case 2: torrent->peer_list->seed_counts[i]--;
                torrent->peer_list->seed_count--;
        case 1: default:
                torrent->peer_list->peer_count--;
                unlock_bucket_by_hash( hash );
                return torrent;
      }
    }
  } else {
    if( (OT_FLAG(peer_dest) & PEER_FLAG_SEEDING ) && !(OT_FLAG(peer) & PEER_FLAG_SEEDING ) ) {
      torrent->peer_list->seed_counts[ base_pool ]--;
      torrent->peer_list->seed_count--;
    }
    if( !(OT_FLAG(peer_dest) & PEER_FLAG_SEEDING ) && (OT_FLAG(peer) & PEER_FLAG_SEEDING ) ) {
      torrent->peer_list->seed_counts[ base_pool ]++;
      torrent->peer_list->seed_count++;
    }
    if( !(OT_FLAG( peer_dest ) & PEER_FLAG_COMPLETED ) && (OT_FLAG( peer ) & PEER_FLAG_COMPLETED ) )
      torrent->peer_list->down_count++;
    if( OT_FLAG( peer_dest ) & PEER_FLAG_COMPLETED )
      OT_FLAG( peer ) |= PEER_FLAG_COMPLETED;

    memmove( peer_dest, peer, sizeof( ot_peer ) );
  }

  unlock_bucket_by_hash( hash );
  return torrent;
}

/* Compiles a list of random peers for a torrent
   * reply must have enough space to hold 92+6*amount bytes
   * Selector function can be anything, maybe test for seeds, etc.
   * RANDOM may return huge values
   * does not yet check not to return self
*/
size_t return_peers_for_torrent( ot_hash *hash, size_t amount, char *reply, int is_tcp ) {
  char        *r = reply;
  int          exactmatch;
  ot_vector   *torrents_list = lock_bucket_by_hash( hash );
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  ot_peerlist *peer_list = torrent->peer_list;
  size_t       index;

  if( !torrent ) {
    unlock_bucket_by_hash( hash );
    return 0;
  }

  if( peer_list->peer_count < amount )
    amount = peer_list->peer_count;

  if( is_tcp )
    r += sprintf( r, "d8:completei%zde10:incompletei%zde8:intervali%ie5:peers%zd:", peer_list->seed_count, peer_list->peer_count-peer_list->seed_count, OT_CLIENT_REQUEST_INTERVAL_RANDOM, 6*amount );
  else {
    *(ot_dword*)(r+0) = htonl( OT_CLIENT_REQUEST_INTERVAL_RANDOM );
    *(ot_dword*)(r+4) = htonl( peer_list->peer_count );
    *(ot_dword*)(r+8) = htonl( peer_list->seed_count );
    r += 12;
  }

  if( amount ) {
    unsigned int pool_offset, pool_index = 0;;
    unsigned int shifted_pc = peer_list->peer_count;
    unsigned int shifted_step = 0;
    unsigned int shift = 0;

    /* Make fixpoint arithmetic as exact as possible */
#define MAXPRECBIT (1<<(8*sizeof(int)-3))
    while( !(shifted_pc & MAXPRECBIT ) ) { shifted_pc <<= 1; shift++; }
    shifted_step = shifted_pc/amount;
#undef MAXPRECBIT

    /* Initialize somewhere in the middle of peers so that
       fixpoint's aliasing doesn't alway miss the same peers */
    pool_offset = random() % peer_list->peer_count;

    for( index = 0; index < amount; ++index ) {
      /* This is the aliased, non shifted range, next value may fall into */
      unsigned int diff = ( ( ( index + 1 ) * shifted_step ) >> shift ) -
                          ( (   index       * shifted_step ) >> shift );
      pool_offset += 1 + random() % diff;

      while( pool_offset >= peer_list->peers[pool_index].size ) {
        pool_offset -= peer_list->peers[pool_index].size;
        pool_index = ( pool_index + 1 ) % OT_POOLS_COUNT;
      }

      memmove( r, ((ot_peer*)peer_list->peers[pool_index].data) + pool_offset, 6 );
      r += 6;
    }
  }
  if( is_tcp )
    *r++ = 'e';

  unlock_bucket_by_hash( hash );
  return r - reply;
}

/* Release memory we allocated too much */
static void fix_mmapallocation( void *buf, size_t old_alloc, size_t new_alloc ) {
  int page_size = getpagesize();
  size_t old_pages = 1 + old_alloc / page_size;
  size_t new_pages = 1 + new_alloc / page_size;

  if( old_pages != new_pages )
    munmap( ((char*)buf) +  new_pages * page_size, old_alloc - new_pages * page_size );
}

/* Fetch full scrape info for all torrents */
size_t return_fullscrape_for_tracker( char **reply ) {
  size_t torrent_count = 0, j;
  size_t allocated, replysize;
  int    i;
  char  *r;

  for( i=0; i<OT_BUCKET_COUNT; ++i )
    torrent_count += all_torrents[i].size;

  /* one extra for pro- and epilogue */
  allocated = 100*(1+torrent_count);
  if( !( r = *reply = mmap( NULL, allocated, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0 ) ) ) return 0;

  memmove( r, "d5:filesd", 9 ); r += 9;
  for( i=0; i<OT_BUCKET_COUNT; ++i ) {
    ot_vector *torrents_list = all_torrents + i;
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      ot_hash     *hash      =&( ((ot_torrent*)(torrents_list->data))[j] ).hash;
      if( peer_list->peer_count || peer_list->down_count ) {
        *r++='2'; *r++='0'; *r++=':';
        memmove( r, hash, 20 ); r+=20;
        r += sprintf( r, "d8:completei%zde10:downloadedi%zde10:incompletei%zdee", peer_list->seed_count, peer_list->down_count, peer_list->peer_count-peer_list->seed_count );
      }
    }
  }

  *r++='e'; *r++='e';

  replysize = ( r - *reply );
  fix_mmapallocation( *reply, allocated, replysize );

  return replysize;
}

size_t return_memstat_for_tracker( char **reply ) {
  size_t torrent_count = 0, j;
  size_t allocated, replysize;
  int    i, k;
  char  *r;

  for( i=0; i<OT_BUCKET_COUNT; ++i ) {
    ot_vector *torrents_list = all_torrents + i;
    torrent_count += torrents_list->size;
  }

  allocated = OT_BUCKET_COUNT*32 + (43+OT_POOLS_COUNT*32)*torrent_count;
  if( !( r = *reply = mmap( NULL, allocated, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0 ) ) ) return 0;

  for( i=0; i<OT_BUCKET_COUNT; ++i )
    r += sprintf( r, "%02X: %08X %08X\n", i, (unsigned int)all_torrents[i].size, (unsigned int)all_torrents[i].space );

  for( i=0; i<OT_BUCKET_COUNT; ++i ) {
    ot_vector *torrents_list = all_torrents + i;
    char hex_out[42];
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      ot_hash     *hash      =&( ((ot_torrent*)(torrents_list->data))[j] ).hash;
      r += sprintf( r, "\n%s:\n", to_hex( hex_out, (ot_byte*)hash) );
      for( k=0; k<OT_POOLS_COUNT; ++k )
        r += sprintf( r, "\t%05X %05X\n", ((unsigned int)peer_list->peers[k].size), (unsigned int)peer_list->peers[k].space );
    }
  }

  replysize = ( r - *reply );
  fix_mmapallocation( *reply, allocated, replysize );

  return replysize;
}

/* Fetches scrape info for a specific torrent */
size_t return_udp_scrape_for_torrent( ot_hash *hash, char *reply ) {
  int          exactmatch;
  ot_vector   *torrents_list = lock_bucket_by_hash( hash );
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

  if( !exactmatch ) {
    memset( reply, 0, 12);
  } else {
    ot_dword *r = (ot_dword*) reply;

    if( clean_single_torrent( torrent ) ) {
      vector_remove_torrent( torrents_list, torrent );
      memset( reply, 0, 12);
    } else {
      r[0] = htonl( torrent->peer_list->seed_count );
      r[1] = htonl( torrent->peer_list->down_count );
      r[2] = htonl( torrent->peer_list->peer_count-torrent->peer_list->seed_count );
    }
  }
  unlock_bucket_by_hash( hash );
  return 12;
}

/* Fetches scrape info for a specific torrent */
size_t return_tcp_scrape_for_torrent( ot_hash *hash_list, int amount, char *reply ) {
  char        *r = reply;
  int          exactmatch, i;

  r += sprintf( r, "d5:filesd" );

  for( i=0; i<amount; ++i ) {
    ot_hash     *hash = hash_list + i;
    ot_vector   *torrents_list = lock_bucket_by_hash( hash );
    ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

    if( exactmatch ) {
      if( clean_single_torrent( torrent ) ) {
        vector_remove_torrent( torrents_list, torrent );
      } else {
        memmove( r, "20:", 3 ); memmove( r+3, hash, 20 );
        r += sprintf( r+23, "d8:completei%zde10:downloadedi%zde10:incompletei%zdee",
          torrent->peer_list->seed_count, torrent->peer_list->down_count, torrent->peer_list->peer_count-torrent->peer_list->seed_count ) + 23;
      }
    }
    unlock_bucket_by_hash( hash );
  }

  *r++ = 'e'; *r++ = 'e';
  return r - reply;
}

#ifdef WANT_TRACKER_SYNC
/* Import Changeset from an external authority
   format: d4:syncd[..]ee
   [..]:   ( 20:01234567890abcdefghij16:XXXXYYYY )+
*/
int add_changeset_to_tracker( ot_byte *data, size_t len ) {
  ot_hash    *hash;
  ot_byte    *end = data + len;
  unsigned long      peer_count;

  /* We do know, that the string is \n terminated, so it cant
     overflow */
  if( byte_diff( data, 8, "d4:syncd" ) ) return -1;
  data += 8;

  while( 1 ) {
    if( byte_diff( data, 3, "20:" ) ) {
      if( byte_diff( data, 2, "ee" ) )
        return -1;
      return 0;
    }
    data += 3;
    hash = (ot_hash*)data;
    data += sizeof( ot_hash );

    /* Scan string length indicator */
    data += ( len = scan_ulong( (char*)data, &peer_count ) );

    /* If no long was scanned, it is not divisible by 8, it is not
       followed by a colon or claims to need to much memory, we fail */
    if( !len || !peer_count || ( peer_count & 7 ) || ( *data++ != ':' ) || ( data + peer_count > end ) )
      return -1;

    while( peer_count > 0 ) {
      add_peer_to_torrent( hash, (ot_peer*)data, 1 );
      data += 8; peer_count -= 8;
    }
  }
  return 0;
}

/* Proposed output format
   d4:syncd20:<info_hash>8*N:(xxxxyyyy)*Nee
*/
size_t return_changeset_for_tracker( char **reply ) {
  size_t allocated = 0, i, replysize;
  int    bucket;
  char   *r;

  /* Maybe there is time to clean_all_torrents(); */

  /* Determine space needed for whole changeset */
  for( bucket = 0; bucket < OT_BUCKET_COUNT; ++bucket ) {
    ot_vector *torrents_list = all_torrents + bucket;
    for( i=0; i<torrents_list->size; ++i ) {
      ot_torrent *torrent = ((ot_torrent*)(torrents_list->data)) + i;
      allocated += sizeof( ot_hash ) + sizeof(ot_peer) * torrent->peer_list->changeset.size + 13;
    }
  }

  /* add "d4:syncd" and "ee" */
  allocated += 8 + 2;

  if( !( r = *reply = mmap( NULL, allocated, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0 ) ) )
    return 0;

  memmove( r, "d4:syncd", 8 ); r += 8;
  for( bucket = 0; bucket < OT_BUCKET_COUNT; ++bucket ) {
    ot_vector *torrents_list = all_torrents + bucket;
    for( i=0; i<torrents_list->size; ++i ) {
      ot_torrent *torrent = ((ot_torrent*)(torrents_list->data)) + i;
      const size_t byte_count = sizeof(ot_peer) * torrent->peer_list->changeset.size;
      *r++ = '2'; *r++ = '0'; *r++ = ':';
      memmove( r, torrent->hash, sizeof( ot_hash ) ); r += sizeof( ot_hash );
      r += sprintf( r, "%zd:", byte_count );
      memmove( r, torrent->peer_list->changeset.data, byte_count ); r += byte_count;
    }
  }
  *r++ = 'e'; *r++ = 'e';

  replysize = ( r - *reply );
  fix_mmapallocation( *reply, allocated, replysize );

  return replysize;
}
#endif

/* Clean a single torrent
   return 1 if torrent timed out
*/
static int clean_single_torrent( ot_torrent *torrent ) {
  ot_peerlist *peer_list = torrent->peer_list;
  size_t peers_count = 0, seeds_count;
  time_t timedout = (int)( NOW - peer_list->base );
  int i;
#ifdef WANT_TRACKER_SYNC
  char *new_peers;
#endif

  /* Torrent has idled out */
  if( timedout > OT_TORRENT_TIMEOUT )
    return 1;

  /* Nothing to be cleaned here? Test if torrent is worth keeping */
  if( timedout > OT_POOLS_COUNT ) {
    if( !peer_list->peer_count )
      return peer_list->down_count ? 0 : 1;
    timedout = OT_POOLS_COUNT;
  }

  /* Release vectors that have timed out */
  for( i = OT_POOLS_COUNT - timedout; i < OT_POOLS_COUNT; ++i )
    free( peer_list->peers[i].data);

  /* Shift vectors back by the amount of pools that were shifted out */
  memmove( peer_list->peers + timedout, peer_list->peers, sizeof( ot_vector ) * ( OT_POOLS_COUNT - timedout ) );
  byte_zero( peer_list->peers, sizeof( ot_vector ) * timedout );

  /* Shift back seed counts as well */
  memmove( peer_list->seed_counts + timedout, peer_list->seed_counts, sizeof( size_t ) * ( OT_POOLS_COUNT - timedout ) );
  byte_zero( peer_list->seed_counts, sizeof( size_t ) * timedout );

#ifdef WANT_TRACKER_SYNC
  /* Save the block modified within last OT_POOLS_TIMEOUT */
  if( peer_list->peers[1].size &&
    ( new_peers = realloc( peer_list->changeset.data, sizeof( ot_peer ) * peer_list->peers[1].size ) ) )
  {
    memmove( new_peers, peer_list->peers[1].data, peer_list->peers[1].size );
    peer_list->changeset.data = new_peers;
    peer_list->changeset.size = sizeof( ot_peer ) * peer_list->peers[1].size;
  } else {
    free( peer_list->changeset.data );

    memset( &peer_list->changeset, 0, sizeof( ot_vector ) );
  }
#endif

  peers_count = seeds_count = 0;
  for( i = 0; i < OT_POOLS_COUNT; ++i ) {
    peers_count += peer_list->peers[i].size;
    seeds_count += peer_list->seed_counts[i];
  }
  peer_list->seed_count = seeds_count;
  peer_list->peer_count = peers_count;

  if( peers_count )
    peer_list->base = NOW;
  else {
    /* When we got here, the last time that torrent
       has been touched is OT_POOLS_COUNT units before */
    peer_list->base = NOW - OT_POOLS_COUNT;
  }
  return 0;
}

/* Clean up all peers in current bucket, remove timedout pools and
   torrents */
void clean_all_torrents( void ) {
  ot_vector         *torrents_list;
  size_t             i;
  static int         bucket;
  ot_time time_now = NOW;

  /* Search for an uncleaned bucked */
  while( ( all_torrents_clean[bucket] == time_now ) && ( ++bucket < OT_BUCKET_COUNT ) );
  if( bucket >= OT_BUCKET_COUNT ) {
    bucket = 0; return;
  }

  all_torrents_clean[bucket] = time_now;

  mutex_bucket_lock( bucket );
  torrents_list = all_torrents + bucket;
  for( i=0; i<torrents_list->size; ++i ) {
    ot_torrent *torrent = ((ot_torrent*)(torrents_list->data)) + i;
    if( clean_single_torrent( torrent ) ) {
      vector_remove_torrent( torrents_list, torrent );
      --i; continue;
    }
  }
  mutex_bucket_unlock( bucket );
}

typedef struct { size_t val; ot_torrent * torrent; } ot_record;

/* Fetches stats from tracker */
size_t return_stats_for_tracker( char *reply, int mode ) {
  size_t    torrent_count = 0, peer_count = 0, seed_count = 0, j;
  ot_record top5s[5], top5c[5];
  char     *r  = reply;
  int       bucket;

  byte_zero( top5s, sizeof( top5s ) );
  byte_zero( top5c, sizeof( top5c ) );

  for( bucket=0; bucket<OT_BUCKET_COUNT; ++bucket ) {
    ot_vector *torrents_list = all_torrents + bucket;
    mutex_bucket_lock( bucket );
    torrent_count += torrents_list->size;
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      if( mode == STATS_TOP5 ) {
        int idx = 4; while( (idx >= 0) && ( peer_list->peer_count > top5c[idx].val ) ) --idx;
        if ( idx++ != 4 ) {
          memmove( top5c + idx + 1, top5c + idx, ( 4 - idx ) * sizeof( ot_record ) );
          top5c[idx].val = peer_list->peer_count;
          top5c[idx].torrent = (ot_torrent*)(torrents_list->data) + j;
        }
        idx = 4; while( (idx >= 0) && ( peer_list->seed_count > top5s[idx].val ) ) --idx;
        if ( idx++ != 4 ) {
          memmove( top5s + idx + 1, top5s + idx, ( 4 - idx ) * sizeof( ot_record ) );
          top5s[idx].val = peer_list->seed_count;
          top5s[idx].torrent = (ot_torrent*)(torrents_list->data) + j;
        }
      }
      peer_count += peer_list->peer_count; seed_count += peer_list->seed_count;
    }
    mutex_bucket_unlock( bucket );
  }
  if( mode == STATS_TOP5 ) {
    char hex_out[42];
    int idx;
    r += sprintf( r, "Top5 torrents by peers:\n" );
    for( idx=0; idx<5; ++idx )
      if( top5c[idx].torrent )
        r += sprintf( r, "\t%zd\t%s\n", top5c[idx].val, to_hex( hex_out, top5c[idx].torrent->hash) );
    r += sprintf( r, "Top5 torrents by seeds:\n" );
    for( idx=0; idx<5; ++idx )
      if( top5s[idx].torrent )
        r += sprintf( r, "\t%zd\t%s\n", top5s[idx].val, to_hex( hex_out, top5s[idx].torrent->hash) );
  } else
    r += sprintf( r, "%zd\n%zd\nopentracker serving %zd torrents\nopentracker", peer_count, seed_count, torrent_count );

  return r - reply;
}

/* This function collects 4096 /24s in 4096 possible
   malloc blocks
*/
size_t return_stats_for_slash24s( char *reply, size_t amount, ot_dword thresh ) {

#define NUM_TOPBITS 12
#define NUM_LOWBITS (24-NUM_TOPBITS)
#define NUM_BUFS    (1<<NUM_TOPBITS)
#define NUM_S24S    (1<<NUM_LOWBITS)
#define MSK_S24S    (NUM_S24S-1)

  ot_dword *counts[ NUM_BUFS ];
  ot_dword  slash24s[amount*2];  /* first dword amount, second dword subnet */
  int       bucket;
  size_t    i, j, k, l;
  char     *r  = reply;

  byte_zero( counts, sizeof( counts ) );
  byte_zero( slash24s, amount * 2 * sizeof(ot_dword) );

  r += sprintf( r, "Stats for all /24s with more than %u announced torrents:\n\n", thresh );

  for( bucket=0; bucket<OT_BUCKET_COUNT; ++bucket ) {
    ot_vector *torrents_list = all_torrents + bucket;
    mutex_bucket_lock( bucket );
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      for( k=0; k<OT_POOLS_COUNT; ++k ) {
        ot_peer *peers =    peer_list->peers[k].data;
        size_t   numpeers = peer_list->peers[k].size;
        for( l=0; l<numpeers; ++l ) {
          ot_dword s24 = ntohl(*(ot_dword*)(peers+l)) >> 8;
          ot_dword *count = counts[ s24 >> NUM_LOWBITS ];
          if( !count ) {
            count = malloc( sizeof(ot_dword) * NUM_S24S );
            if( !count )
              goto bailout_cleanup;
            byte_zero( count, sizeof( ot_dword ) * NUM_S24S );
            counts[ s24 >> NUM_LOWBITS ] = count;
          }
          count[ s24 & MSK_S24S ]++;
        }
      }
    }
    mutex_bucket_unlock( bucket );
  }

  k = l = 0; /* Debug: count allocated bufs */
  for( i=0; i < NUM_BUFS; ++i ) {
    ot_dword *count = counts[i];
    if( !counts[i] )
      continue;
    ++k; /* Debug: count allocated bufs */
    for( j=0; j < NUM_S24S; ++j ) {
      if( count[j] > thresh ) {
        /* This subnet seems to announce more torrents than the last in our list */
        int insert_pos = amount - 1;
        while( ( insert_pos >= 0 ) && ( count[j] > slash24s[ 2 * insert_pos ] ) )
          --insert_pos;
        ++insert_pos;
        memmove( slash24s + 2 * ( insert_pos + 1 ), slash24s + 2 * ( insert_pos ), 2 * sizeof( ot_dword ) * ( amount - insert_pos - 1 ) );
        slash24s[ 2 * insert_pos     ] = count[j];
        slash24s[ 2 * insert_pos + 1 ] = ( i << NUM_TOPBITS ) + j;
        if( slash24s[ 2 * amount - 2 ] > thresh )
          thresh = slash24s[ 2 * amount - 2 ];
      }
      if( count[j] ) ++l;
    }
    free( count );
  }

  r += sprintf( r, "Allocated bufs: %zd, used s24s: %zd\n", k, l );

  for( i=0; i < amount; ++i )
    if( slash24s[ 2*i ] >= thresh ) {
      ot_dword ip = slash24s[ 2*i +1 ];
      r += sprintf( r, "% 10ld %d.%d.%d.0/24\n", (long)slash24s[ 2*i ], (int)(ip >> 16), (int)(255 & ( ip >> 8 )), (int)(ip & 255) );
    }

  return r - reply;

bailout_cleanup:

  for( i=0; i < NUM_BUFS; ++i )
    free( counts[i] );

  return 0;
}

size_t remove_peer_from_torrent( ot_hash *hash, ot_peer *peer, char *reply, int is_tcp ) {
  int          exactmatch;
  size_t       index;
  ot_vector   *torrents_list = lock_bucket_by_hash( hash );
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  ot_peerlist *peer_list;

  if( !exactmatch ) {
    unlock_bucket_by_hash( hash );

    if( is_tcp )
      return sprintf( reply, "d8:completei0e10:incompletei0e8:intervali%ie5:peers0:e", OT_CLIENT_REQUEST_INTERVAL_RANDOM );

    /* Create fake packet to satisfy parser on the other end */
    ((ot_dword*)reply)[2] = htonl( OT_CLIENT_REQUEST_INTERVAL_RANDOM );
    ((ot_dword*)reply)[3] = ((ot_dword*)reply)[4] = 0;
    return (size_t)20;
  }

  peer_list = torrent->peer_list;
  for( index = 0; index<OT_POOLS_COUNT; ++index ) {
    switch( vector_remove_peer( &peer_list->peers[index], peer, index == 0 ) ) {
      case 0: continue;
      case 2: peer_list->seed_counts[index]--;
              peer_list->seed_count--;
      case 1: default:
              peer_list->peer_count--;
              goto exit_loop;
    }
  }

exit_loop:

  if( is_tcp ) {
    size_t reply_size = sprintf( reply, "d8:completei%zde10:incompletei%zde8:intervali%ie5:peers0:e", peer_list->seed_count, peer_list->peer_count - peer_list->seed_count, OT_CLIENT_REQUEST_INTERVAL_RANDOM );
    unlock_bucket_by_hash( hash );
    return reply_size;
  }

  /* else { Handle UDP reply */
  ((ot_dword*)reply)[2] = htonl( OT_CLIENT_REQUEST_INTERVAL_RANDOM );
  ((ot_dword*)reply)[3] = peer_list->peer_count - peer_list->seed_count;
  ((ot_dword*)reply)[4] = peer_list->seed_count;

  unlock_bucket_by_hash( hash );
  return (size_t)20;
}

#ifdef WANT_ACCESS_CONTROL
void accesslist_reset( void ) {
  free( accesslist.data );
  byte_zero( &accesslist, sizeof( accesslist ) );
}

int accesslist_addentry( ot_hash *infohash ) {
  int em;
  void *insert = vector_find_or_insert( &accesslist, infohash, OT_HASH_COMPARE_SIZE, OT_HASH_COMPARE_SIZE, &em );

  if( !insert )
    return -1;

  memmove( insert, infohash, OT_HASH_COMPARE_SIZE );

  return 0;
}
#endif

int trackerlogic_init( const char * const serverdir ) {
  if( serverdir && chdir( serverdir ) ) {
    fprintf( stderr, "Could not chdir() to %s\n", serverdir );
    return -1;
  }

  srandom( time(NULL) );

  /* Initialize control structures */
  byte_zero( all_torrents, sizeof( all_torrents ) );

  mutex_init( );

  return 0;
}

void trackerlogic_deinit( void ) {
  int i;
  size_t j;

  /* Free all torrents... */
  for(i=0; i<OT_BUCKET_COUNT; ++i ) {
    if( all_torrents[i].size ) {
      ot_torrent *torrents_list = (ot_torrent*)all_torrents[i].data;
      for( j=0; j<all_torrents[i].size; ++j )
        free_peerlist( torrents_list[j].peer_list );
      free( all_torrents[i].data );
    }
  }
  byte_zero( all_torrents, sizeof (all_torrents));
  byte_zero( all_torrents_clean, sizeof (all_torrents_clean));

  mutex_deinit( );
}